The present invention relates to hydronic systems in which zoning circulators move heated water from a furnace to various heating zones of a building or to one or more heating zones and a heat exchanger and tank for heating domestic hot water.
For example, a heating system might have three heating zones, each with a separate zoning circulator, and a fourth zoning circulator moving heated water to a heat exchanger in a hot water tank. Usually, each zoning circulator has its own control box, which has supplied to it high voltage (115 VAC) lines for powering the zoning circulator and low voltage control lines from a thermostat.
It is often desirable in hydronic systems to be able to assure that if the associated thermostat is calling for the zoning circulator to operate then the other zoning circulators are prevented from operating. This permits, for example, the circulator operating the hot water tank, or a circulator that heats a particularly cold part of a house, to have higher priority than other zones.
A known control system for zoning circulators, sold by Argo, provides this priority function from a central control box in which the first of the relays is hardwired to have the highest priority, and whichever circulator is controlled via that relay is given the highest priority. To change priorities requires an electrician to change the wiring at the control box.